Changing SessionService to have a BaseSessionService, not being one.

chrome/browser/sessions/session_service_utils.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/sessions/session_service_utils.h"
 
+const int gMaxPersistNavigationCount = 6;
+
 SessionWindow::WindowType WindowTypeForBrowserType(Browser::Type type) {
   switch (type) {
     case Browser::TYPE_POPUP:
       return SessionWindow::TYPE_POPUP;
     case Browser::TYPE_TABBED:
       return SessionWindow::TYPE_TABBED;
   }
   NOTREACHED();
   return SessionWindow::TYPE_TABBED;
 }
 
 Browser::Type BrowserTypeForWindowType(SessionWindow::WindowType type) {
   switch (type) {
     case SessionWindow::TYPE_POPUP:
       return Browser::TYPE_POPUP;
     case SessionWindow::TYPE_TABBED:
       return Browser::TYPE_TABBED;
   }
   NOTREACHED();
   return Browser::TYPE_TABBED;
 }